1. Field of the Invention
The present invention relates to a method of fabricating a liquid crystal display (LCD) device, and more particularly, to a method for forming a pattern of an LCD device using a printing method.
2. Discussion of the Related Art
Among ultra thin flat panel display devices having a display screen several centimeters thick, LCD devices have been widely used for notebook computers, monitors, spaceships, aircraft, and so on due to their features and advantages of a low driving voltage, low power consumption, portability, and the like.
The LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the substrates. Generally, a thin film transistor and a pixel electrode are formed on the lower substrate, and a light-shielding layer, a color filter layer and a common electrode are formed on the upper substrate.
The LCD device includes various elements, and a number of process steps are repeated to form the elements. Particularly, a photolithographic process has been used to pattern such various elements in various shapes.
However, because the photolithographic process requires a mask of a predetermined pattern and a light or radiation source, the fabricating cost increases correspondingly. Also, because the photolithographic process includes exposure and development processes, the process steps are complicated and the process time becomes long.
Under these circumstances, a new method for forming a pattern has been required to solve the drawbacks of the photolithographic process. As a result, a printing method has been suggested.
In the printing method, to form a desired pattern, a desired material is coated on a printing roll and then transferred onto a substrate by rotating the printing roll. Hereinafter, a related art printing method will be described in more detail with reference to the accompanying drawings.
FIGS. 1A to 1C are process views illustrating a related art printing method.
First, as shown in FIG. 1A, a pattern material 20 is coated on a printing roll 30 using a printing nozzle 10. In this case, because a blanket 35 is attached to the printing roll 30, the pattern material is coated on the blanket 35.
Then, as shown in FIG. 1B, the printing roll 30 is rotated on a printing plate 40 provided with a concave portion 43 and a convex portion 46. In this case, some pattern material 20a is transferred onto the convex portion 46 of the printing plate 40, and a predetermined pattern 20b is formed on the blanket 35 of the printing roll 30 by the remaining pattern material 20b. 
Afterwards, as shown in FIG. 1C, the printing roll 30 is rotated on a substrate 50 to transfer the pattern 20b onto the substrate 50.
Because the aforementioned related art printing method does not need a photolithographic process such as exposure and development processes, the cost is reduced and the process steps are simplified. Therefore, the related art printing method is very suitable for mass production.
However, in the aforementioned related art printing method, the pattern material 20 coated on the blanket 35 of the printing roll 30 may be in contact with the concave portion 43 of the printing plate 40. In this case, a problem occurs in that a precise pattern is not formed.
Referring to FIG. 2, problems of the related art printing method will be described in more detail.
As shown in FIG. 2A, when the printing roll 30 whose blanket 35 is coated with the pattern material 20 is rotated on the printing plate 40 provided with the concave portion 43 and the convex portion 46, the pattern material 20 may be in contact with the concave portion 43 of the printing plate 40.
The pattern material 20 may be in contact with the concave portion 43 of the printing plate 40 by swelling of the blanket 35 attached to the printing roll 30. Alternatively, the pattern material 20 may be in contact with the concave portion 43 of the printing plate 40 when the concave portion of the printing plate 40 has a large size to form a large sized pattern.
If the pattern material 20 is in contact with the concave portion 43 of the printing plate 40 as shown in FIG. 2A, some pattern material 20a is transferred onto the convex portion 46 and at the same time some pattern material 20b is transferred onto the concave portion 43 as shown in FIG. 2B. For this reason, a pattern material 20c remaining on the blanket 35 of the printing roll 30 is not formed in the desired pattern, and no pattern material is formed in a region A. As a result, it is difficult to form a precise pattern.
In particular, if some pattern material 20b is transferred onto the concave portion 43 by contact, the pattern material in all directions as well as the pattern material in contact with the concave portion 43 is spaced apart from the blanket 35 and transferred onto the concave portion 43.
In other words, if the pattern material is in contact with the concave portion 43 of the printing plate 40, a problem occurs in that an undesired pattern material is transferred onto the concave portion 43. Another problem occurs in that a pattern material to be transferred onto the concave portion cannot be predicted at all.